The design and development of scalable, efficient photothermal evaporator systems that reduce microplastic pollution are highly desirable. Herein, a sustainable bacterial nanocellulose (BNC)-based self-floating bilayer photothermal foam (PTF b ) is designed that eases the effective confinement of solar light for efficient freshwater production via interfacial heating. The sandwich nanoarchitectured porous bilayer solar evaporator consists of a top solar-harvesting blackbody layer composed of broad-spectrum active black titania (BT) nanoparticles embedded in the BNC matrix and a thick bottom layer of pristine BNC for agile thermal management, the efficient wicking of bulk water, and staying afloat. A decisive advantage of the BNC network is that it enables the fabrication of a lightweight photothermal foam with reduced thermal conductivity and high wet strength. Additionally, the hydrophilic three-dimensional (3D) interconnected porous network of BNC contributes to the fast evaporation of water under ambient solar conditions with reduced vaporization enthalpy by virtue of intermediated water generated via a BNC− water interaction. The fabricated PTF b is found to yield a water evaporation efficiency of 84.3% (under 1054 W m −2 ) with 4 wt % BT loading. Furthermore, scalable PTF b realized a water production rate of 1.26 L m −2 h −1 under real-time conditions. The developed eco-friendly BNC-supported BT foams could be used in applications such as solar desalination, contaminated water purification, extraction of water from moisture, etc., and thus could address one of the major present-day global concerns of drinking water scarcity.

Enhanced fluorescence was achieved by tuning the photonic band gaps in colloidal photonic crystals and host–guest chemistry.

Herein, we demonstrate a simple, highly efficient, and cost-effective clean water generation strategy that can be implemented in the geographical locations deprived of freshwater resources. We captured and purified the atmospheric water utilizing CaCl2 as a deliquescent material followed by solar thermal desalination with an engineered-photothermal nanocomposite sheet (E-PNS). The E-PNS was prepared using Mn2+ ion promoted oxygen vacancy (VO) rich black anatase TiO2 nanoparticles as filler and poly­(vinylidene fluoride) as the polymer matrix. The developed E-PNS exhibits an excellent radiation absorption of ∼98.5% covering the entire solar spectrum (250–2500 nm) and has interconnected micropores that facilitate efficient solar–thermal heat and mass transfer. Hence, the reported clean water generation strategy achieves a high solar to thermal conversion efficiency of 90% under light irradiation (solar simulator, intensity 1.13 kW m–2), which is 2.2 times higher when compared to water itself. Further, real-time analysis of an E-PNS integrated all-in-one water from air generator prototype showed a clean water generation rate of 0.365 kg m–2 h–1, i.e., ∼2.2 L m–2 day–1, under direct solar irradiation (∼1.06 kW m–2), thereby offering a very promising technological solution for the production of clean water in water-scarce regions.

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